#include<bits/stdc++.h>
using namespace std;
double n;
int main()
{
	scanf("%lf", &n);
	double l = -100, r = 100;
	while (r - l > 1e-8)
	{
		double mid = (l + r) / 2;
		if (mid * mid * mid <= n) l = mid;
		else r = mid;
	}
	printf("%.6lf\n", l);
	return 0;
}